Method and apparatus for information storage



Jan. 20, 1970 W. S. M EWAN ET AL METHOD AND APPARATUS FOR INFORMATIONSTORAGE Filed Jan. 31, 1968 INVENTORS. WILLIAM S. MCEWAN PETER R.HAMMOND BY v ROY MILLER ATTORNEYS.

United States Patent Ofilce 3,491,364 Patented Jan. 20, 1970 3,491,364METHOD AND APPARATUS FOR INFORMATION STORAGE William S. McEwan and PeterR. Hammond, China Lake,

Califi, assignors to the United States of America asrepresented by theSecretary of the Navy Filed Jan. 31, 1968, Ser. No. 702,092 Int. Cl.G01d 9/12 U.S. Cl. 34621 8 Claims ABSTRACT OF THE DISCLOSURE A systemfor information storage which comprises a film having a recordingsurface coated or impregnated with a heat sensitive mixture consistingof a pair of compounds, one an electron acceptor and the other anelectron donor, which may be dispersed in an immiscible matrix, and ahot stylus in contact therewith and movable there to. As the stylus ismoved over the treated film surface a color appears due to the action ofheat on the mixture leaving a record on the film of the movement of thestylus.

BACKGROUND OF THE INVENTION The present invention relates to a methodand apparatus for information storage by utilizing a mixture composed oftwo mutual compounds which becomes colored when heated and fades oncooling.

The prior art discloses color forming chemical reaction recorders usingpaper treated with phenolphthalein and a stylus material composed ofsodium lead or sodium amalgam which reacts with the chemical in thepaper to produce a color change. Memories have also been stored onspecial photographic plates which can be located by beam deflectors.Transparent liquid or jelly-like compositions which when subjected toelectric impulses of a certain magnitude provide visual displays undereither visible or ultraviolet light. The chemical recorders aresensitive and depend upon the quality and manner of handling thereactants in order to produce color recordings. The photographic andvarious electronic devices available are expensive and generally requirespecial training to operate. The present invention provides a simple andpractical memory storage system by use of a mixture of pairs ofpreselected compounds which is heat sensitive, changing color accordingto temperature with no chemical reaction occurring between the pairs ofcompounds.

SUMMARY In accordance with the present invention paper film was thinlycoated on one surface with a heat sensitive mixture composed ofpreselected acceptor-donor compounds in compatible matrixes and a hotstylus was moved over the coated surface. As the stylus moved along theheat caused the coating to change color leaving a record on the film ofthe movement of the stylus.

The colors of the acceptor-donor systems used on at least one surface ofthe film herein vanish on cooling. The early work of Charles K. Tinklerwho described the disappearance of color on freezing some mixtures ofnitrocompounds with amines in his paper entitled A Series of Mixtures ofNitro-Compounds and Amines Which Are Colored in the Liquid State Only,Chem. Soc. (London) J. 1913, pp. 2171-79, provided the first examples ofthe color systems developed and used herein. The color system developedby the present inventors considerably extends the class of materials andprovides a rationale for selecting further systems. For eachacceptordonor chemical examined, the disappearance in one system wasoften accompanied by disappearance in others. The basis of the colorchange, namely, a donor to acceptor change-transfer transition even whenno bond is formed between these molecules, is not new to the study ofmolecular complexes. The following table is a list of mixtures of thepairs of compounds which formed stable complexes giving the colors ofthe melts and of the solids.

TABLE I.COLOR CHANGES OF SOME ACGEPTOR-DONOR MIXTURES Solution orMlxture melt color Color of solid Diphenylarnine-palinitrobenzene RedWhite.

Diphenylamme-p-chloronitroben- Orange Do.

zene.

Tetranitromethane-hexamethyl- Red-orange Do.

benzene.

Tetranitrometheme-naphthalene Yellow-orange. Do.

Tr n tromesitylene-dimethylaniline do D0.

Trimtromesitylene-anthracene Yellow Do.

Hexanltrodiphenyl-pyrene Red Pale cream.

Hexamtrodiphenyl-anthracene Magenta White.

p-Dinltrobenzene-triphenylamine l Red Do.

1,3,5-tr1mtrobenzene-triphenyl- Red Very pale pink.

amine.

p-Chloranil-triphenylamine Blue-green Pale cream.

Tetraeyanoethylene-tetra-i-propyl- V'olet White.

benzene.

Tetraeyanoethylene-p-di-i-butyl- Red-orange. Do.

benzene.

p-Dinitrobenzene-tetramethyl-2- Orange Do.

tetrazene.

p-Nitroanisole-tetrakis(dirnethyl- Red D0.

amino) ethylene.

Nitrobenzenetetrakis(dimethyl- Magenta D0.

amino) ethylene.

p-Chloronitrobenzene-tetrakis Violet D o.

(dimethylamino) ethylene.

Aeridinetetrakis(dimethylamino) Red Do.

ethylene.

In all cases the changes shown in the above table were distinct. Allcolors were produced immediately on mixing and were stable untilsolidified. The change from a deep violet liquid of the mixture oftetracyanoethylene and tetra-i-propylbenzene to a clean, whitecrystalline solid was at once distinct. Microscopic slides of thediphenylamine and p-chloronitrobenzene, trinitromesitylene andanthracene, hexanitrodiphenyl and anthracene, triphenyl amine andp-dinitrobenzene, and tetracyanoethylene and tetra-i-propylbenzenemixtures, although colored in the hot liquid state, were Colorless byboth transmitted and reflected light. The colors of the solids were thecolors of the original components, although a very faint pink could beobtained on rapid freezing of the deep red trinitrobenzene andtriphenylamine liquid mixtures. Heating of any of the solids in theabove table immediately produced the original color and the cyclewithout doubt could be repeated innumerable times. The conditionessential for the loss of color is seen to be the separation of acceptorand donor molecules, generally into two phases in the solid, a behaviortypical of systems showing simple eutectic diagrams. Diffractionpatterns are clearly those of the pure materials in the mixtures and noadditional lines are observed. The proportion of acceptor and donormolecules in contact, and hence capable of contributing to theabsorption intensity, must be the relatively few at' crystal interfaces.Melting point diagrams and X-ray crystal studies confirm the lack ofcompound formation. It is the general object of this invention toprovide an information storage device which is economical and practicaland may be cycled an infinite number of times without wearing out.Another object is to provide a recording apparatus and method which isuseful for the continuous recording of information over a widetemperature range with no chemical reaction occurring between thecomponents. Other objects, features, and many of the attendantadvantages of this invention will become readily appreciated byreference to the following description when considered in connectionwith the accompanying draw- 3 BRIEF DESCRIPTION OF THE DRAWINGSDESCRIPTION OF THE INVENTION Referring now to FIGS. 1 and 2 there isshown a recording apparatus wherein a film is drawn from supply spool 11over platen 12, r llers 13 to reroller 14. A stylus 15 adapted to beheated rests on the surface of film 10. Stylus 15 is carried by arecording arm 16 and is pivoted to shaft 17 at point 18. As shaft 17moves over its predetermined range, stylus 15 moves across film 10producing a record as indicated by 19. Stylus 15 consists of a metal andis heated by electrical means (not shown), or other suitable means,provided in shaft 17. Film 10 shown in FIG. 2 is coated on its recordingsurface 20 within a thin layer 21 of a mixture consisting of apreselected pair of acceptor-donor chemicals in a compatible matrixwhich in solution at certain temperatures is colored and which at thesolidus temperature exhibits a loss of color.

A laser beam may replace the stylus since a aser acts by producing heatin a small area.

The coating was prepared by mixing together in about equal amounts theacceptor and donor compounds in a compatible solvent such astetrahydrofuran, dichloromethane or similar solvents. The acceptor anddonor compounds may also be mixed together without a solvent. At roomtemperature the mixtures stayed in solution and were colored whenbrushed onto sheets of white paper. When the solvent evaporated, themixture solidified and the color vanished. Other materials such asplastics to which the mixture will adhere or into which the mixture canbe absorbed may be used for the film, and other means of coating thematerial may be used such as by immersion into the mixture, by spraying,etc.

In operation, as heated stylus 15 moves along the recording surface 20of film 10 a visible record 19 is formed on layer 21. This is due to theheat from the stylus melting the layer which in melt or solution iscolored. Upon returning to the solidus temperature, the colordisappeared. The apparatus of FIG. 1 has the advantage of recordinginformation temporarily and then being resuable since return to thesolid state erases the record.

A second embodiment of the invention is shown in FIGS. 3 and 4 whereinlike numbers in the drawings indicate identical structures throughoutthe embodiments of the invention. The recording film 10a consists ofuncoated, light-colored paper. The stylus has been modified, and nowdesignated 15a consists of a housing 22 closed on one end and providedwith a capillary tube 23 containing a mixture of the same preselectedpairs of acceptor-donor chemicals as the coating 21 on film 10 in theembodiment shown and described in FIG. 1. In operation as stylus 15amoves over the surface of film 10a it deposits the mixture in melt formwhich is colored. As film 10a is moved along on reroller 14 the solventevaporates and the color fades. Upon gentle warming of film 10a thecolor reappears making the information visible. The housing andcapillary tube may be of any suitable material such as metal or someplastics. This embodiment provides a permanent memory storage apparatuswhich at solidus temperatures is invisible and on gentle warming becomesvisible.

Obviously many modifications and variations of the present invention arepossible n t g t of the above teachings.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed is:

1. An apparatus for recording information on a dry film in the form of acolored melt which on solidification fades and reappears upon gentlewarming comprising:

a dry light-colored film and a stylus in contact with and movablerelative to said film; said stylus containing a mixture consistingessentially of a pair of acceptor-donor chemicals which are colored inthe liquid state, in contact with said film and producing a record incolor on the film of the movement of the stylus relative thereto;

said pair of acceptor-donor chemicals being selected from the groupconsisting of diphenylamine and p-dinitrobenzene; diphenylamine andp-chloranil; diphenylamine and chloronitrobenzenc; diphenylamine andp-chloronitrobenzene; tetranitromethane and hexamethylbenzene;tetranitromethane and naphthalene; trinitromesitylene anddimethylaniline; trinitromesitylene and anthracene; hexanitrodiphenyland pyrene; hexanitrodiphenyl and anthracene; p-dinitrobenzene andtriphenylamine; 1,3,5-trinitrobenzene and triphenylamine; p-chloraniland triphenylamine; tetracyanoethylene and tetra-i-propylbcnzene;tetracyanoethylene and p-dii-buty1benzene; p-dinitrobenzene andtetramethyl-2-tetrazene; p-nitroanisole andtetrakis(dimethylamino)ethylene; nitrobenzene andtetrakis(dirnethylamino)ethylene; p-chloronitrobenzene andtetrakis(dimethylamino)ethylene and acridine and tetrakis(dimethylamino)ethylene.

2. The apparatus of claim 1 wherein said stylus contains a mixtureconsisting of diphenylamine and p-dinitrobenzene.

3. The apparatus of claim 1 wherein said stylus contains a mixture, ofdiphenylamine and p-chloranil.

4. The apparatus of claim 1 wherein said stylus contains diphenylamineand p-chloronitrobenzene.

5. The apparatus of claim 1 wherein the stylus contains a mixture ofp-dinitrobenzene and triphenylamine.

6. The apparatus of claim 1 wherein the stylus contains a mixture oftetracyanoethylene and tetra-i-propylbenzene.

7. The apparatus of claim 1 wherein the stylus contains a mixture oftetracyanoethylene and p-di-t-butylbenzene.

8. An apparatus for temporarily recording information in the form of acolored melt which at its solidus temperature vanishes comprising a filmhaving at least one surface coated with a mixture consisting of a pairof donor-acceptor chemicals;

a heated stylus adjacent and movable relative to said coated surface ofsaid film; said stylus being heated to the temperature at which saidcoating melts when adjacent to said surface and producing a record incolor on said coated surface of the movement of the stylus relativethereto;

said pair of acceptor-donor chemicals being selected from the groupconsisting of diphenylamine and p-dinitrobenzene; diphenylamine andp-chloranil; diphenylamine and chloronitrobenzenc; diphenylamine andp-chloronitrobenzene; tetranitromethane and hexamethylbenzene;tetranitromethane and naphthalene; trinitromesitylene anddimethylaniline; trinitromesitylene and anthracene; hexanitrodiphenyland pyrene; hexanitrodiphenyl and anthracene; p-dinitrobenzene andtriphenylamine; 1,3,5-trinitr0benzene and triphenylamine; p-chloraniland triphenylamine; tetracyanoethylene and and tetra-i-propylbenzene;tetracyanoethylene and p-di-i-butylbenzene; p-dinitrobenzene andtetramethyl-Z-tetrazene; p-nitroanisole andtetrakis(dimethylamin0)ethylene; nitrobenzene andtetrakis(dimethylamino)ethylene; p-chlo- 5 6 ronitrobenzene andtet1-akis(dimethylamino)ethylene 1,844,199 2/ 1932 Bicknell et a1 346-76X and acridine and tetrakis (dimethylamino)ethy1ene. 1,939,232 12/1933Sheppard et a1 346-76 X 2,631,918 3/1953 Kozak 346135 X References CitedUNITED STATES PATENTS 1,351,071 8/1920 Silvermanet a1. 346135X 1,402,4421/1922 Porter 10621 21;3 6 6, 3

5 JOSEPH W. HARTARY, Primary Examiner

